Treatise On Applied Analytical Chemistry(Vol-1)

202

FERRO-CHROME

SILICON FERRO-MANGANESE

(Silico -spiegeleisen)

Silicon ferro-manganese may be regarded as a product intermediate to
ferro-silicon and ferro-manganese. It is obtained in the blast furnace or
the electric furnace, the latter yielding especially pure products. Its
analysis includes the following:

1. Determination of the Silicon.—As silicon ferro-manganese is
attacked either not at all or with difficulty by acids, the silicon should be
estimated by the methods given for the determination of silicon in ferro-
silicon.

2. Determination of the Manganese.—As in ferro-silicon.

3. Determination of the Carbon.—By direct combustion in a current
of oxygen (see Iron, i,b).

4. Determination of the Phosphorus and Sulphur.—As in ferro-
silicon.

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Silicon ferro-manganese obtained from the blast furnace contains about
20% Mn, 10-12% Si (occasionally 20%), 2-2-5% c> 0-01-0-2% P, and some-
times minimal traces of sulphur.

That from the electric furnace may contain 35-75% Mn, 20-35% Si, 0-6-1-5%
C, 0-01-0-06% P, 0-02-0-03% S, and sometimes traces of coppqr, aluminium, etc.

FERRO-CHROME

Ferro-chrome may be prepared in the blast furnace or the electric
furnace and serves for making chrome steels. Its analysis includes :

1. Determination of the Chromium.—The sample is best attacked
by the following methods.1

(a) FUSION WITH SODIUM HYDROXIDE AND PEROXIDE. 03-0'5 gram of
the very finely powdered sample are mixed, in a silver crucible or dish and
with a silver spatula, with 2 grams of sodium hydroxide in minute frag-
ments, the mixture being covered with 4 grams of sodium peroxide and
heated to incipient fusion, the flame being then removed to prevent the
reaction from becoming too violent; the heat developed in the reaction
rapidly melts all the contents of the dish or crucible. A little more sodium
peroxide is added to the fused mass, the latter being heated gradually to
fusion when the reaction begins to abate. After about 10 minutes, about
5 grams of sodium peroxide are mixed in and the mass heated rather more
energetically so as to maintain it in a state of quiet fusion for 20-30 minutes,
after which a further quantity of 5-6 grams of the peroxide is added and

1 G. Gallo (Rend. R. Accademia Lincei, 1907, XVI, p. 58) proposes an ingenious
method for attacking ferrous products with a high content of chromium. It consists
in electrolysing at a temperature of 80-85° a 15% potassium chloride solution rendered
slightly alkaline with potassium hydroxide, using as cathode a platinum wire and as
anode the metal to be analysed. All the chromium in the latter is thus transformed into
alkaline chromate. and